Process for producing phthalaldehyde

ABSTRACT

A process of the present invention produces phthalaldehyde by allowing at least one compound selected from o-xylylene glycol and o-xylylene oxide to react with nitric acid. The amount of nitric acid is from about 0.2 to about 20 moles per mole of the at least one compound selected from o-xylylene glycol and o-xylylene oxide. The present invention can efficiently produce phthalaldehyde from easily available raw materials.

TECHNICAL FIELD

[0001] The present invention relates to a process for producingphthalaldehyde (i.e. o-phthalaldehyde). Phthalaldehyde is a compoundwidely used as a raw material or intermediate for agriculturalchemicals, pharmaceutical drugs and cosmetics and is specificallyimportant as a raw material for insecticides for industrial use.

BACKGROUND ART

[0002] Phthalaldehyde has been produced by, for example, a process ofreducing corresponding phthaloyl dichloride, a process of directlyoxidizing a methyl group in a side chain of o-xylene, or a process ofhydrolyzing α,α,α′,α′-tetrachloroxylene. However, these processes eachhave various disadvantages and are not industrially or commerciallysatisfactory.

[0003] For example, the process of reducing phthaloyl dichloriderequires an expensive raw material as well as an expensive palladiumcompound as a catalyst and exhibits a low yield. The process of directlyoxidizing a methyl group in a side chain of o-xylylene is performed by aliquid phase process or a gas phase process, each of which cannotexhibit a sufficient yield. The process of hydrolyzingα,α,α′,α′-tetrachloroxylene requires hardly availableα,α,α′,α′-tetrachloroxylene as a raw material and often yieldsby-products in the hydrolysis procedure.

DISCLOSURE OF INVENTION

[0004] Accordingly, an object of the present invention is to provide aprocess for efficiently producing phthalaldehyde from easily availableraw materials.

[0005] After intensive investigations to achieve the above object, thepresent inventors have found that, by allowing easily availableo-xylylene glycol or o-xylylene oxide to react with nitric acid,phthalaldehyde can be produced in a high yield and thereby high-purityphthalaldehyde can be obtained at low cost without using a hardlyhandleable chemical substance such as a halogen derivative as a rawmaterial and/or a metallic catalyst. The present invention has beenaccomplished based on these findings.

[0006] Specifically, the present invention provides a process forproducing phthalaldehyde, comprising the step of allowing at least onecompound selected from o-xylylene glycol and o-xylylene oxide to reactwith nitric acid to thereby yield phthalaldehyde. In this process, theamount of nitric acid is about 0.2 to about 20 moles per mole of the atleast one compound selected from o-xylylene glycol and o-xylylene oxide.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] [o-Xylylene Glycol and o-Xylylene Oxide]

[0008] At least one compound selected from o-xylylene glycol ando-xylylene oxide is used as a reaction component (substrate) in thepresent invention. The benzene ring of o-xylylene glycol and o-xylyleneoxide may further have one to four of other substituents. Suchsubstituents include, for example, methyl, ethyl, propyl, isopropyl,butyl, isobutyl, t-butyl, and other alkyl groups, of which C₁-C₄ alkylgroups are preferred; fluorine, chlorine, bromine, and other halogenatoms; methoxy, ethoxy, isopropoxy, and other alkoxy groups, of whichC₁-C₄ alkoxy groups are preferred; methoxycarbonyl, ethoxycarbonyl, andother alkoxycarbonyl groups, of which C₁-C₄ alkoxy-carbonyl groups arepreferred; acetyl group, benzoyl group, and other acyl groups; acetoxygroup, and other acyloxy groups; hydroxyl group; carboxyl group; nitrogroup; unsubstituted, mono-substituted, or di-substituted amino groups;nitro group; and cyano group.

[0009] Each of o-xylylene glycol and o-xylylene oxide can be used aloneor in combination. When they are used in combination as a mixture, themixing ratio thereof is not specifically limited.

[0010] [Nitric Acid]

[0011] Nitric acid is used as an oxidizing agent in the presentinvention. Such nitric acid is not specifically limited, andcommercially available one can be used. Nitric acid can be diluted withwater or an inert organic solvent before use. The amount of nitric acidis, for example, from about 0.2 to about 20 moles, and preferably fromabout 1 to about 10 moles per mole of the substrate.

[0012] The process of the present invention does not always require acatalyst, but a catalyst can be used, for example, in order to shorten areaction time. The catalyst includes, for example, compounds eachcontaining any of metallic elements having an atomic number of 23 to 29(V, Cr, Mn, Fe, Co, Ni, and Cu). Examples of such metallic compoundsare, of the metals, nitrates, chlorides, sulfates, carbonates, and othersalts; and oxides. Preferred catalysts include, for example, vanadiumcompounds. The amount of the catalyst can be appropriately set dependingon, for example, the type of the catalyst and the concentration ofnitric acid and is generally from about 0.002 to about 0.1 part byweight relative to 1 part by weight of the substrate. An initiator suchas sodium nitrite, nitrogen dioxide, or benzoyl peroxide and/orazobisisobutyronitrile known as a radical initiator can be used in thereaction.

[0013] [Reaction]

[0014] The reaction is performed in the presence of, or in the absenceof, a solvent. Such solvents include, for example, water; acetic acid,other organic acids, hydrochloric acid, perchloric acid, sulfuric acid,other inorganic acids, and other acids; dioxane, and other ethers; andmixtures of these solvents. A reaction rate often increases when themedium has a higher acidity. Preferred solvents include a water-aceticacid mixture, and other mixtures of water and an acid. In this case, thereaction rate can be controlled by regulating the ratio of water to theacid. When a solvent mixture of water and acetic acid is used, the ratioof water to acetic acid in a reaction system is, for example, such thatthe former/the latter is from about 0/100 to about 99/1.

[0015] A reaction temperature can be appropriately selected dependingon, for example, the type of the substrate and is, for example, fromabout 20° C. to about 200° C., preferably from about 50° C. to about150° C., and more preferably from about 65° C. to about 120° C. Thereaction can be performed at normal atmospheric pressure or under apressure (under a load). The reaction time varies depending on, forexample, the reaction temperature and is generally from about 0.1 toabout 12 hours, and preferably from about 0.2 to about 8 hours. Thereaction can be performed according to any system such as a batchsystem, semi-batch system or continuous system.

[0016] According to the process of the present invention, the reactioncan selectively and efficiently oxidize a methylene carbon atom at thealpha position of the benzene ring of the substrate even under mildconditions to thereby yield corresponding phthalaldehyde. After thecompletion of the reaction, a reaction product can be separated andpurified by a separation means such as filtration, concentration,distillation, extraction, crystallization, recrystallization, and columnchromatography or any combination of these separation means.

Industrial Applicability

[0017] The process of the present invention can efficiently producephthalaldehyde from easily available and easily handleable raw materialswithout the use of halogen-atom-containing compounds and other hardlyhandleable compounds and metallic catalysts. Accordingly, the presentinvention is excellent both in economical efficiency and workability andis suitable as a process for the industrial production ofphthalaldehyde.

EXAMPLES

[0018] The present invention will be illustrated in further detail withreference to several examples below, which are not intended to limit thescope of the invention.

Example 1

[0019] In a 1000-ml three-neck flask equipped with a thermometer, areflux condenser and a stirrer were placed 50 g of o-xylylene glycol,78.4 g of 60% by weight nitric acid, 170.1 g of water, and 201.5 g ofacetic acid. The mixture was raised in temperature to 70° C. on an oilbath and was stirred under these conditions for 1 hour. After cooling,the reaction mixture was analyzed by gas chromatography to find that theraw material o-xylylene glycol was completely absent and thatphthalaldehyde was formed in a yield of 84%. The obtained reactionmixture was extracted with two portions of toluene, the organic layerwas distilled and thereby yielded phthalaldehyde in a yield of 67% onthe basis of o-xylylene glycol. Gas chromatographic analysis revealedthat phthalaldehyde had a purity of 98.8%. In addition, phthalide wasformed in a yield of 12%.

Example 2

[0020] The procedure of Example 1 was repeated, except that the reactionwas performed at 60° C. for 2 hours. As a result, phthalaldehyde wasobtained in a yield of 76% after the completion of the reaction and wasobtained in a yield of 65% with a purity of 98.2% after extraction anddistillation. In addition, phthalide was formed in a yield of 16%.

Example 3

[0021] The procedure of Example 1 was repeated, except that the reactionwas performed at 80° C. for 0.5 hour. As a result, phthalaldehyde wasobtained in a yield of 87% after the completion of the reaction and wasobtained in-a yield of 72% with a purity of 99.0% after extraction anddistillation. In addition, phthalide was formed in a yield of 10%.

Example 4

[0022] In a 1000-ml three-neck flask equipped with a thermometer, areflux condenser and a stirrer were placed 50 g of o-xylylene oxide,87.5 g of 60% by weight nitric acid, 163.8 g of water, and 198.8 g ofacetic acid. The mixture was raised in temperature to 70° C. on an oilbath and was stirred under these conditions for 1 hour. After cooling,the reaction mixture was analyzed by gas chromatography to find that theraw material o-xylylene oxide was completely absent and thatphthalaldehyde was formed in a yield of 86%. Phthalide was formed in ayield of 13% as a by-product. The obtained reaction mixture wasextracted with two portions of toluene, the organic layer was distilledand thereby yielded phthalaldehyde in a yield of 70% on the basis ofo-xylylene glycol. Gas chromatographic analysis revealed thatphthalaldehyde had a purity of 99.0%.

Example 5

[0023] The procedure of Example 4 was repeated, except that the reactionwas performed at 60° C. for 2 hours. As a result, phthalaldehyde wasobtained in a yield of 76% after the completion of the reaction and wasobtained in a yield of 63% with a purity of 98.2% after extraction anddistillation. In addition, phthalide was formed in a yield of 15%.

Example 6

[0024] The procedure of Example 4 was repeated, except that the reactionwas performed at 80° C. for 0.5 hour. As a result, phthalaldehyde wasobtained in a yield of 89% after the completion of the reaction and wasobtained in a yield of 74% with a purity of 99.2% after extraction anddistillation. In addition, phthalide was formed in a yield of 9%.

Example 7

[0025] In a 1000-ml three-neck flask equipped with a thermometer, areflux condenser and a stirrer were placed 13.3 g of o-xylylene glycol,36.7 g of o-xylylene oxide, 85.1 g of 60% by weight nitric acid, 165.5 gof water, and 199.5 g of acetic acid. The mixture was raised intemperature to 70° C. on an oil bath and was stirred under theseconditions for 1 hour. After cooling, the reaction mixture was analyzedby gas chromatography to find that the raw material o-xylylene glycolwas completely absent and that phthalaldehyde was formed in a yield of84%. The obtained reaction mixture was extracted with two portions oftoluene, the organic layer was distilled and thereby yieldedphthalaldehyde in a yield of 67% on the basis of o-xylylene glycol. Gaschromatographic analysis revealed that phthalaldehyde had a purity of98.8%. In addition, phthalide was formed in a yield of 11%.

Example 8

[0026] In a 1000-ml three-neck flask equipped with a thermometer, areflux condenser and a stirrer were placed 50 g of o-xylylene glycol,39.2 g of 60% by weight nitric acid, 197.6 g of water, and 213.2 g ofacetic acid. The mixture was raised in temperature to 70° C. on an oilbath and was stirred under these conditions for 2 hours. After cooling,the reaction mixture was analyzed by gas chromatography to find that theraw material o-xylylene glycol was completely absent and thatphthalaldehyde was formed in a yield of 60%. In addition, phthalide(yield: 6%) and an ester of the raw material were formed as by-products.The obtained reaction mixture was extracted with two portions oftoluene, the organic layer was distilled and thereby yieldedphthalaldehyde in a yield of 45% on the basis of o-xylylene glycol. Gaschromatographic analysis revealed that phthalaldehyde had a purity of95.0%. In addition, phthalide was formed in a yield of 10%.

Example 9

[0027] In a 1000-ml three-neck flask equipped with a thermometer, areflux condenser and a stirrer were placed 50 g of o-xylylene oxide,43.8 g of 60% by weight nitric acid, 203.1 g of water, and 220.6 g ofacetic acid. The mixture was raised in temperature to 70° C. on an oilbath and was stirred under these conditions for 4 hours. After cooling,the reaction mixture was analyzed by gas chromatography to find that theraw material o-xylylene oxide was completely absent and thatphthalaldehyde was formed in a yield of 50%. The obtained reactionmixture was extracted with two portions of toluene, the organic layerwas distilled and thereby yielded phthalaldehyde in a yield of 35% onthe basis of o-xylylene oxide. Gas chromatographic analysis revealedthat phthalaldehyde had a purity of 93.0%. In addition, phthalide wasformed in a yield of 9%.

1. A process for producing phthalaldehyde, comprising the step ofallowing at least one compound selected from o-xylylene glycol ando-xylylene oxide to react with nitric acid to thereby yieldphthalaldehyde.
 2. The process for producing phthalaldehyde according toclaim 1, further comprising using 0.2 to 20 moles of nitric acid permole of the at least one compound selected from o-xylylene glycol ando-xylylene oxide.